This application claims priority from European Patent application No. 13198643.2 filed on Dec. 19, 2013, the entire disclosure of which is hereby incorporated herein by reference.
The present invention concerns a magnetic centring device for components of small size, particularly for centring a pivotally mounted component. A particular field of application of the invention concerns timepiece mechanisms.
The introduction of active magnetic components, such as permanent magnets and parts made of soft ferromagnetic material, into timepiece mechanisms represents a significant technical challenge because of the extremely reduced dimensions and high spatial precision required to accomplish chronometric functions in a reliable manner.
Most natural or synthetic magnetic materials are inhomogeneous on a millimeter scale or less, which makes it difficult to control magnetic field localization and intensity on this scale. In particular, permanent micro-magnets having the highest magnetic energy intensity, for example SmCo or NdFeB micro-magnetics, are typically manufactured from powders of chemical elements from the rare earth family, their granular structure having dimensions of between 1 and 100 microns. The homogeneity of the magnetic field generally decreases as it approaches the grain scale.
The utilisation of magnetic components for rotating elements of timepiece movements or mechanisms, for example as described in WO Patent No 2012/0662524 and WO Patent No 2012/062523 or of other micromechanical mechanisms, such as measuring or control instruments, is advantageous because it makes it possible to create large localized forces accompanied by low friction.